It is well known to remove solid contaminants of all sizes from a fluid, frequently a liquid, by a centrifugal separator in which a substantially vertically-mounted, high speed rotor includes a contaminant-depositing container, (more conveniently referred to simply as a contaminant container) through which the fluid is passed and in which solid contaminants are separated from the fluid to deposit on the container wall from which they can be periodically removed or the container replaced. Such a centrifugal cleaner may have its rotor driven by external coupling to an engine or like rotary plant with which used, which results in a complex and expensive arrangement, or may, as is more usual, be driven by causing the fluid applied to the contaminant container under pressure to exit by way of tangentially directed nozzle means, the reaction to which spins the rotor at high speed essential for efficient centrifugal separation. Such a fluid-cleaner, in which the rotor is driven by the fluid being cleaned, is what is referred to herein as a self-powered centrifugal separator.
Such self-powered centrifugal separators are used with internal combustion engines of a variety of types and sizes to effect separation of particulate contaminants from lubricating oil circulated through components of any engine by way of ducts formed within the engine block. Examples of such cleaners are to be found in GB 735658, GB 1089355 and GB 2193123.
Self-powered centrifugal separators are, by definition, by-pass devices in which any lubricating oil which is supplied at substantially the same pressure as to other engine components passes through, and effects rotation of, the contaminant container by losing all of its energy in the process and is able only to return to a collecting reservoir of the engine under gravity. Such separators are therefore always employed in combination with conventional full-flow barrier filters by way of which the lubricant is pumped at high pressure to the working components of the engines, and a proportion of this lubricant is directed to the centrifugal cleaner.
Traditionally an engine block has been made with a prepared region adapted to receive a filter assembly thereon, and with ducts surfacing at such regions for supplying lubricant to, and taking it from the filter assembly. The area of engine block surface that is available for mounting an additional centrifugal separator is small and hitherto emphasis has been placed on providing a maximum cross-sectional area for a drain duct, so that lubricant can drain freely under gravity, while providing the high pressure supply through an external, but exposed, line.
It is known to make cleaning assemblies incorporating both full-flow barrier filters and self-powered centrifugal separators in a single mounting arrangement, having a carrier manifold or block which is mounted on, and forms the interface for liquid passage with, the engine block. Examples of these are given in GB 876299, GB 2160449 and GB 2160796. However, in many engine designs, having existing simple, full-flow filter provisions, it is preferable to have separately mounted full-flow filter and centrifugal separator.
One of the benefits of employing a centrifugal separator is that the container can operate for long intervals before it becomes filled with sediment requiring the container to be cleaned or replaced. However, even though its operation is not essential to continual operation of the engine, at least in the short term, due to the lubricant by-passing the working components of the engines, it is still necessary with traditional designs to clean or replace the container at regular maintenance times when the engine is stopped, notwithstanding that the container of the centrifugal separator may not need attention (such attention requires removal of a cover containing the container and replacement of any seals etc.)
Because the lubricant path through the arrangement by-passes that supplying the engine components, it should be possible to remove, clean and/or change the contaminant container whilst the engine runs, but when the container is rotating at high speed and ejecting lubricant within the cover this is clearly extremely undesirable. Furthermore, as it is usually a simple matter to determine when a container has stalled, that is ceased to rotate, through becoming filled with sediment, there is the possibility of an operative removing the cover in order to remove the stationary container without realizing or remembering that the inlet to the container is connected to the source of high pressure lubricant for the engine. Such inadvertent removal of the rotor would not only discharge lubricant about the exterior of the engine but also starve the engine components of more lubricant than is normally by-passed by the separator.
The danger to engine functionality posed by uncontrollable release of lubricant is, of course, also compromised by any high pressure liquid supply line, exposed externally of the engine, becoming damaged.
Thus whereas such self-powered centrifugal separator arrangements operate for long intervals without attention, their presence may involve a small but quantifiable risk of engine damage through accident or inadvertent operation not connected with the functioning of the separator per se.
Notwithstanding that such an engine is just one example of a machine in which liquid, such as a lubricant, is circulated by pump pressure and requires separation of particulate contaminants, it is an object of the present invention to provide, for a machine in which a liquid such as lubricating oil is circulated through internal supply and drain ducts, a self-powered centrifugal separator which offers improved operational functionality and safety than arrangements known hitherto.